Extensive Studies on the Synthesis and Characterization of π-Arene Chromium Complexes

We report an efficient synthesis of a series of new (η6‑arene)Cr(CO)3 complexes via ligand exchange strategy under thermal conditions using chromium hexacarbonyl and readily accessible arene feedstocks. We optimized the previously reported procedures and found that the high excess of arenes usually employed is not required to access the π-arene chromium complexes in high yields. Consequently, the revised procedure simplifies the purification of chromium tricarbonyl complexes bearing arenes with high boiling points. The reaction is amenable to provide (η6‑arene)Cr(CO)3 complexes decorated with various functional groups. Notably, the novel and already reported chromium complexes with missing spectroscopic characterization were fully characterized by nuclear magnetic resonance (NMR), infrared (IR) spectroscopies and high‑resolution mass spectrometry (HRMS). Besides, we report the structure of 20 chromium complexes characterized via X-ray crystallography. The potential application of these πarene chromium complexes has also been exploited towards the selective construction of poly(hetero)aryls possessing a single chromium tricarbonyl unit through SNAr and Suzuki-Miyaura cross-coupling reactions. This work is meant to be a practical guide for the synthesising of π-arene chromium complexes and filling the gap in their spectroscopic characterization.